Physiologic concentrations of magnesium and placental apoptosis: prevention by antioxidants

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Abstract
Objective: To identify the role of physiologic magnesium concentrations on the induction of placental apoptosis in vitro and test the anti-apoptotic action of antioxidants. Methods: Placental tissue was obtained from normal pregnancies after cesarean delivery. Placental explants were incubated with increasing concentrations of extracellular magnesium (range 0–2.0 mM). Placental apoptosis was evaluated by tissue morphology, DNA fragmentation, cytokeratin-18 neoepitope formation, and cleavage of plasminogen activator inhibitor type 2. Results: Physiologic concentrations of extracellular magnesium stimulated placental apoptosis. Magnesium stimulated apoptosis within the physiologic range (0.8–1.2 mM) (n = 6, P < .001) and was associated with cleavage of plasminogen activator inhibitor type 2 and cytokeratin-18 neoepitope formation. These data implicate caspase activation in the transduction of the magnesium-induced apoptotic signal. Therapeutic concentrations of vitamin C, vitamin E, and acetylcysteine (all at 25 μg/mL) inhibited DNA fragmentation and attenuated cleavage of plasminogen activator inhibitor type 2 and cytokeratin-18 neoepitope formation. Conclusion: Magnesium-induced placental apoptosis is a potent mechanism of placental degeneration in vitro and may represent an important regulator of placental tissue dynamics in vivo. The ability of antioxidants to prevent magnesium-induced placental apoptosis implicates oxidation–reduction-dependent signaling events in this process. Furthermore, these findings provide a basis for further studies of antioxidants in mitigating the adverse effects of preeclampsia.

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